Title: New Methodology for Designing Self-Compacting Concrete
Author(s): Aaron W. Saak, Hamlin M. Jennings, and Surendra P. Shah
Publication: Materials Journal
Appears on pages(s): 429-439
Keywords: cement paste; concrete; slump
A new segregation-controlled design methodology is introduced for self-compacting concrete (SCC). The theory suggests that aggregate segregation is governed by the yield stress, viscosity, and density of the cement paste matrix. The concept of a rheological self-flow zone (SFZ) for concrete is introduced where aggregate segregation is avoided, yet the concrete has a high workability. The applicability of the theory is studied by systematically changing the rheology of the cement paste matrix of fresh concrete. The yield stress and viscosity of three different types of pastes incorporating silica fume and a cellulose thickening agent is measured as a function of density. A U-tube apparatus is then used to determine the SFZ for concrete made with the different cement paste compositions. The results suggest that the new segregation control design theory can be used to produce SCC. The slump of concrete produced using this new methodology was 29 cm (11 in.), with no segregation of coarse aggregate even at the periphery of the slumped material.